Error in Update child record EF Core 3.0 The association between entities has been severed but the relationship is either marked as 'Required'

I'm using EF Core version: 3.0 Database provider: Microsoft.EntityFrameworkCore.SqlServer

I have two tables: PROFILO (master) and PROFILOTITOLODISTUDIO (details) this is the model:

PROFILO MODEL

publicpartialclassProfilo{publicProfilo(){ProfiloTitoloDiStudio=newList<ProfiloTitoloDiStudio>();}[Key]publicGuidIdProfilo{get;set;}[Required][StringLength(256)]publicstringNome{get;set;}[StringLength(256)]publicstringCognome{get;set;}[InverseProperty("IdProfiloNavigation")]publicvirtualIList<ProfiloTitoloDiStudio>ProfiloTitoloDiStudio{get;set;}}

PROFILOTITOLODISTUDIO MODEL

publicpartialclassProfiloTitoloDiStudio{[Key]publicintIdProfiloTitoloDiStudio{get;set;}publicGuidIdProfilo{get;set;}[Required][StringLength(256)]publicstringDenominazioneCorsoStudio{get;set;}[ForeignKey(nameof(IdProfilo))][InverseProperty(nameof(Profilo.ProfiloTitoloDiStudio))]publicvirtualProfiloIdProfiloNavigation{get;set;}}

The IdProfilo foreign key in the PROFILOTITOLODISTUDIO tablemust be NOT NULL

In the controller's Edit action I receive the object with the fields bounded by the view as an input, even if I don't change any value, thesavechanges () always returns the error:

InvalidOperationException: The association between entities 'Profilo' and 'ProfiloTitoloDiStudio' with the key value '{IdProfilo: 45c42779-39b6-4047-91d1-12253a79b7f6}' has been severed but the relationship is either marked as 'Required' or is implicitly required because the foreign key is not nullable. If the dependent/child entity should be deleted when a required relationship is severed, then setup the relationship to use cascade deletes.

this is the save code:

publicasyncTask<IActionResult>Edit(Profilo profiloinput){var _profiloDB =await _dbcontext.Profilo.Include(p => p.ProfiloTitoloDiStudio).SingleOrDefaultAsync(p => p.IdProfilo== profiloinput.IdProfilo);

            _profiloDB.Nome= profiloinput.Nome;
            _profiloDB.Cognome= profiloinput.Cognome;


            _profiloDB.ProfiloTitoloDiStudio= profiloinput.ProfiloTitoloDiStudio;var x =await _dbcontext.SaveChangesAsync();}

I am not breaking any relationship between PROFILE and PROFILOTITOLODISTUDIO I am simply trying to make an update on the child table, the IDPROFILO foreign key in the profile object.ProfiloTitoloDiStudio is perfectly enhanced !!!